How do I resolve meshing and mesh quality errors or warnings?
Element QualityThe element quality refers the shape of the element.
Low quality elements may come from a number of sources including but not limited to:
- Gaps between slabs,
- Small spaces between columns,
- Columns very close to the edge of a slab but not quite on the edge, etc.
In some instances, the quality may be at a level that could be ignored e.g. 4.99% (only 0.01% lower than the 5% limit).
In other instances, the question of whether to ignore the warning or not is less obvious and engineering judgement should be applied (e.g. 4.80%, 3.85%, etc.).
How to adjust the user limit?
You could adjust the user limit to decrease the threshold where the limit is reported, however, this should only be done to a reasonable extent.
What to do is your Engineering judgement however, we recommend that the more critical warnings (i.e. those approaching 0.1%) are resolved.
Critical levels will yield an error and must be resolved (i.e. under 0.1%).
This is achieved via the Home ribbon > Project group > Model Settings > Validation page
Locating the error or warning
Double clicking on the error or warning reported in the Project Workspace > Status tree, the software will take you to the area with the issue.
Sometimes the item in question is behind the foremost object in view and may therefore be difficult to find. You may need to rotate the model or hide some items via Scene Content.
The selected item will be marked with a Blue Arrow pointing at its location.
You can also open the Solver View of the floor from the Project Workspace > Structure tree and then select the item in question in the Status tab to aid you in finding the item.
The screenshots below are an example of the above.
The mesh elements are created automatically by Tekla Structural Designer.
In order to address these warnings, they need to be investigated and the model altered accordingly to allow the software to create better mesh elements.
I can't alter my model geometry, what else can I try?There are a few other ways to aid Tekla Structural Designer to create better meshing.
This includes but is not limited to:
- You could move columns to be right on the edge of slabs as opposed to very close to them
- Replace two columns close to each other with one single, larger column
- Ensure slabs are connected along the whole edge
You may also consider altering the Mesh properties by selecting Structure in the Project Workspace > Structure tree and changing the Mesh properties in the Properties window.
Why is it important to address these warnings?The mesh quality refers to the ratio of the longest side of an FE shell to the shortest and also considers the ratio of largest to smallest internal dimension, which is a measure of element distortion. In a perfect shell the short side would equal the long side and the mesh quality would be 100%.
When the mesh quality is poor, the deformed shells can be extremely stiff relative to the surrounding shells. This can lead to unusual moment spikes etc. Also excessively stiff elements can cause ill-conditioning, see related article.
To prevent this we generate
- Warnings when the quality falls below 5%
- Error (which prevent the analysis taking place) at 0.1%.